Method for protection of cellulosic fibrous material from attack by micro-organisms



2,753,574; Patented Sept. 18, lihfit METHOD FOR PROTECTION OF CELLULOSIC FIBROUS MATERIAL FROM ATTACK BY MICRO-URGANISMS Andreas Ruperti, Arlesheim, Switzerland, assignor to Ciba Limited, Basel, Switzerland, in Swiss firm No Drawing. Application July 7, 1952, Serial No. 297,563

Claims priority, application Switzerland July 10, 1951 19 Claims. (Cl. 117-103) This invention relates to the protection of cellulosic fibrous material from attack by microorganisms.

It is known that cellulosic fibrous material, for example fabrics and yarns, can be treated with hardenable aminoplasts in order to improve the materialfrom various points of view. Thus it is possible for example, among other things, to increase the resistance to creasing and swelling of fabrics. The effects obtained dependto a large extent upon the fact that the hardenable aminoplasts, alone or in association with the cellulose, form an insoluble more or less rigid three dimensional framework which takes place by far-reaching cross-linking of the resin. The known treatment for increasing the resistance to' creasing and swelling of fabrics, is carried out in such a manner that the fabric is impregnated with solutions or emulsions of aminoplasts, which may also contain hardening accelerators, followed by drying and finally by a treatment at elevated temperature, for example at about 120460 C. in order to effect hardening of the resin. The cross-linking which takes place in this method of hardening, and which is necessary for the above specified purposes, also has disadvantageous consequences, for example the mechanical properties of the fibrous material are deteriorated, handle and hardness are influenced in an unfavourable manner and the capacity for being. dyed by direct dyestuffs is reduced or mayeven be entirely removed.

It is due to the disadvantageous effect, chiefly upon the mechanical properties, of the known impregnation process, that although it is known that by means of a treatment of cellulosic fibrous material with aminoplasts a degree of protection against attack by micro-organisms can be achieved, this possibility has hitherto remained without practical importance. It is obvious that a treatment of yarns which causes a reduction of the tear resistance of the material, is extremely disadvantageous and cannotbe used in practice when the yarns are intended for use for example for the making of fish netting,.cords or ropes and that such a treatment is also unsuitable for application. to finished products of this type, that is to say fish nets on ships cables.

The present invention is based on the discovery of a water-resistant impregnation for cellulosic fibrous material whiclr renders said material resistant to the attack of micro-organisms, with far-reaching retentionof the textile properties of the material, when the impregnation with aqueous solutions or emulsions of hardenable aminoplasts iscarried out in such a manner that after the impregnation of the fibrous material and mechanical removal of the excess of impregnating liquid, the aminoplasts are converted into the water-insoluble condition,-.in and upon the fibres, without completely removing the water derived from the impregnating liquid and retained by the fibres, until the resin condensation is completed,v so that the condensation proceeds in the presence of water.

The success of the process depends upon the exploita tion of the surprising and hitherto unknown fact that the. condensation of hardenable aminoplasts, according to the condensation conditions selected, leads to end stages wl ich differ from one another and by which the treated fibrous material is influenced in difierent ways. According to the hitherto customary process, with drying and heat hardening, as already stated above, the tear resistance of the fibres and their capacity for being dyed with direct dyestuffs is reduced. In contradistinction to this, accord ing to the present invention, the possibility is provided of carrying out the condensation of the aminoplasts in a different manner and proceeding to an end stage, namely in the presence of water which is retained by the fibres from the impregnating liquid, at which a resin so condensed does not influence the tear resistance of the fibres and their capacity for being dyed with direct dyestuffs or influences it only to an inconsiderable extent but protects the treated fibres against attack by micro-organisms.

The reason why the two end stages referred to above diifer from one another has not hitherto been ascertained. The differences can be recognized only by the differences in tear resistance of the impregnated fibres and by their varying capacity for being dyed with direct dyestuffs.

The fixing of the aminoplasts by the method of the invention can be carried out entirely without drying of the impregnated fibrous material or with partial drying thereof before or during the fixing operation, provided that such drying takes place uniformly Without any disturbance due to wandering of the condensation product and that it is not carried out to such an extent that the affinity of the fibres for direct dyestuffs is reduced. The simplest mode of execution consists in that the fibrous material impregnated with a solution or emulsion, after squeezing out or hydroextracting, that is to say after the mechanical removal of the excess of bath liquid, is maintained for a long time without positive drying and with prevention of premature drying out. The period for wh'ch the material needs to be kept in this condition varies between a few elevated temperature, for example at 80 C.

minutes and a few days. It depends on one hand on the aminoplast and reaction accelerator employed and on the other hand on the temperature of storage. The storage can take place at ordinary room temperature or at it has proved to be advantageous to store the impregnated fibrous material in a closed vessel because by this means premature drying out can be avoided. When the fixing of the resin is complete the fibrous material is well rinsed in the usual way and then dried. As stated above,

in accordance with the process of the invention, a partial drying can take place before or during the fixation of the resin. In thiscase care must be taken that there is no local over-drying of the treated textile material and that no wandering of unfixed resin takes place during the drying, as otherwise the success of the treatment is detrimentally affected. A uniform drying can be carried out for example in such a manner that the impregnated fibrous material is stored in a drying chamber through which is passed a current of air of predetermined relato remove the water to such an extent that only about 5 per cent. remains above the normal water content of the fibres and still to fix the resin in the manner required according to the present invention. in one experiment in which the water was removed up to the retention of 2 /2 per cent. above the normal water content of the fibres, only a small decrease was observed of the capacity for being dyed with direct dyestutfs, with practically complete retention of the strength characteristics.

In order to determine whether the resin fixation has taken place by the method of the present invention, a comparison of the tear resistances of the treated and untreated material will give the required information. Material treated according to the invention exhibits approximately the same tear resistance as untreated material, whereas fibrous material impregnated according to the customary process suffers a loss of strength of up to 30 per cent. Testing of the capacity of the fibres for being dyed with direct dyestuffs can advantageously be carried out with the blue dyeing dyestutf Direct Sky Blue green shade (Colour Index No. 518). Fibrous material treated according to the present invention is dyed by this dyestuif equally strongly or even somewhat more strongly than untreated material, whereas fibrous material impregnated according to the customary process is only faintly dyed by this dyestufi.

The expression hardenable aminoplasts as used with respect to the present invention is to be understood as including hardenable, if desired etherified, carbamide and melamine resins, which are either water soluble or also of limited water solubility and which are obtained in the known manner by condensation of formaldehyde with compounds such, for example, as urea, thiourea, cyanamide, dicyandiamide, biguanide, melamine, formoguanamine, acetoguanamine and so on and also mixtures of such compounds, and furthermore their alkyl and acyl compounds. Especially good results are obtained by the use of water-soluble condensation products of melamine and formaldehyde, for example a condensation product of limited water solubility from one mol of melamine and about three mols formaldehyde.

By condensation products of limited water-solubility there are to be understood in the sense of the present invention those colloidal intermediate stages which occur by continuing the condensation beyond the crystalline methylol stage. They are characterised by the property that they are precipitated from their concentrated aqueous solutions by the addition of water (cf. Kolloid- Zeitschrift, vol. LVII, October-December 1931, page 233, left-hand column).

The condensation products of unlimited water-solubility are used in the form of aqueous solutions, while those of limited water-solubility are used either in the form of solutions of the condensation products which have been rendered soluble with the aid of acids, or in the form of emulsions. Advantageously reaction accelerators are added both to the solutions and to the emulsions. As such there are concerned the generally customary hardening catalysts, for example acids, such as hydrochloric acid, sulphuric acid or formic acid; also salts of strong acids with weak bases can be used, for example ammonium salts of strong inorganic or organic acids, such as ammonium chloride, ammonium sulphate, ammonium nitrate, ammonium oxalate or ammonium lactate. In the use of solutions of aminoplasts to which acids are added, care is to be taken that these solutions are freshly prepared because on account of certain changes which take place in the solutions on standing, their suitability for the purposes of the present invention is affected very detrimentally.

The baths for the impregnation according to the invention advantageously contain about 3-10 per cent. of aminoplast, either in solution or emulsion. The impregnation is advantageously carried out in such a manner that the aminoplasts are deposited upon the fibres in a quantity of about 3-10 per cent., preferably about 5 per cent, of the weight of the fibre.

. The impregnation can take place by the customary processes and with the use of the customary plant.

The present process can be used in the case of all cellulosic fibres. It is especially suitable for the treatment of natural celluloses, as for example cotton or bast fibres. The invention can be applied with advantagfi;

to the impregnation of loose material, yarns and materials in an intermediate stage of conversion into yarn, such as condensed sliver, which are intended for working up to fish netting or ships cables, or of the finished goods themselves. The treatment of fabrics of cellulosic fibres can also be carried out according to the present invention.

By combining this impregnation with an impregnation with other protective agents, as for example tanning agents, fungicides or bactericides, the protection against the attack of micro-organisms can be still further increased.

The following examples illustrate the invention:

Example 1 Coarse cotton twist intended for the manufacture of fish netting is immersed, in hank-form, in a freshly prepared solution containing 60 grams of condensation product of limited water-solubility from 1 mol of melamine and 3 mols of formaldehyde, 24 grams of formic acid, l gram of a non-ionogenic wetting agent per litre, at room temperature, turned several times in the bath and compressed in order to expel the air contained in the yarn, hydroextracted to 170 per cent. of the original yarn Weight and stored for a long time (overnight or for 1-3 days) in a closed vessel. It is thereupon rinsed, first with dilute ammonia solution and then very thoroughly with water, and dried.

Mechanical properties, swelling capacity and capacity for being dyed with cotton dyestuffs remain practically unchanged, however, the yarn has become resistant to the bacterial attack which takes place in water. A four weeks treatment in sapropel at 37 C. gave the following. tear or tensile strength values for untreated yarn and yarn treated according to Example 1.

Example 2 Bleached cotton yarn is immersed in a freshly prepared aqueous emulsion containing per litre 35 grams of a condensation product of limited watersolubility from 1 mol of melamine and 3 mols of formaldehyde 0.4 gram of gelatine 3.5 grams of ammonium chloride and turned several times therein for about 5 minutes with repeated compression. After hydroextracting to 170 per cent. of the original yarn weight, the product is heated for 2 hours in a closed vessel to 80 C. and then thorough ly rinsed with cold water. After 24 hours washing in running water, the yarn exhibits a N-content of 2.56 per cent. and has a good resistance to attack by the microorganisms of sapropel.

dyestuffs and mechanical properties remain unchanged i with an identical N-content after washing of 2.56 perv compared with the starting material.

If the resin fixation is carried out not as described in this example but in the customary manner by drying with subsequent hardening (6 minutes at C.), then,

Dyeing capacity with cotton perature, no noteworthy fixation of the resin takes place. The N-content after washing with water amounts only to 0.27 per cent. and there is no protective effect against sewage.

The condensation product of limited water-solubility, used in the preceding examples, can be obtained for example as follows:

A solution of 1 mol of melamine in about 3 mols of aqueous formaldehyde solution is heated, at a pH of 8-9, to about 80 C. until 1 part of a cooled test portion, treated with 3-4 parts of cold water just gives a turbidity. Then the solution is evaporated to dryness in the customary manner, for example in a spray drier.

Example 3 In the manufacture of cotton yarn for fish netting the condensed sliver is impregnated with a solution containing per litre 50 grams of a condensation product of unlimited water-- solubility from 1 mol of melamine and about 2 mol, of formaldehyde and 5 grams of ammonium chloride.

In order to obtain a uniform impregnation it is to be recommended to use boiled off condensed sliver or to add to the impregnating solution 1 gram per litre of a nonionogenic wetting agent.

The impregnation is advantageously carried out in wet twisting on the twisting machine, in such a manner that the sliver, before twisting, is passed through the specified impregnating solution instead of through water.

The wet spools of twisted sliver are kept overnight in a closed drying chamber at about 80 C. while continuously in a wet condition and are subsequently rinsed or directly dried.

A yarn subjected to this preservative treatment, on immersion in sapropel at 37 C. shows no loss of strength after 8 weeks, whereas untreated yarn even after 4 Weeks has lost all strength.

Example 4 Cotton fabric is treated on the foulard with an impregnating solution freshly prepared according to EX- ample l. The impregnated fabric, squeezed off to 190 per cent., is partially dried in a drying chamber at 75 C. until about 50 per cent. of the water present has evaporated. (The water present being 190l00%=90%, about 50% of the latter is about 45%, so that there is a retention of about 45% of the water, calculated on the weight of the fabric.) During the drying moist air is blown into the drying chamber in order to avoid local over-drying. After about 4 hour the desired degree of drying has been attained and the condensation product is fixed on the fibre in a water-insoluble manner. The textile properties of the fabric have not been changed but it has become to a far reaching extent rot-proof. On burial in moist compost earth with 30 per cent. water content for two weeks at a temperature of 30 C., practically no loss of strength takes place.

If, prior to the described treatment, the fabric is impregnated with a l per cent. aqueous solution of sodium pentachlorphenolate and dried, it also becomes protected against surface growing fungi. Instead of the melamine formaldehyde condensation product used in this example a condensation product from urea and formaldehyde ora mixed condensation product can be used.

What I claim is:

l. A process for imparting to cotton fibrous material a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous impregnating liquid of a. melamine formaldehyde condensation product which contains a hardening accelerator, which comprises afterimpregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

2. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous impregnating liquid of a melamine formaldehyde condensation product which contains a hardening accelerator, which comprises afterimpregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

3. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation pro tecting such material from attack by microorganisms, Without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility which solution is freshly prepared with the aid of an acid, which comprises after impregnating the material and removing maohanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation prod uct in and upon the fibre into the water-insoluble con dition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

4. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which solution is freshly prepared with the aid of formic acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the waterinsoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin conden sation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of Water originating from the impregnating liquid.

5. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protesting such material from attack by microorganisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous emulsion of a melamine formaldehyde condensation product, of limitcd Water solubility from 1 mol of melamine and about- 3 mols of formaldehyde which emulsion contains also an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

6. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of said material, by treating it with an aqueous solution of a melamine formaldehyde condensation product of unlimited water solubility from 1 mol of melamine and about 2 mols of formaldehyde which solution also contains an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation prodnet in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight ofthe fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

7. A process for imparting to cottom fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility which solution is freshly prepared with the aid of an acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at room temperature.

8. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which solution is freshly prepared with the aid of formic acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation in completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at room temperature.

9. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous emulsion of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which emulsion contains also an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed,- so that the condensation into the Water insoluble state is actually conducted in the presence of water originating from the lmpregnating liquid, said hardening being carried out at room temperature.

10. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a Water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous solution of a melamine formaldehyde condensation product of un-' limited water solubility from 1 mol of melamine and about 2 mols of formaldehyde which solution also contains an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the waterinsoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at room temperature.

11. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility which solution is freshly prepared with the aid of an acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at elevated temperature.

12. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which solution is freshly prepared with the team aid of formic acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the Water-insoluble condition with retention of at least about 45 calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of Water originating from the impregnating liquid, said hardening being carried out at elevated tern perature.

13. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous solution of a melamine formaldehyde condensation product of unlimited water solubility from 1 mol of melamine and about 2 mols of formaldehyde which solution also contains an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the waterinsoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at elevated temperature.

14. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility which solution is freshly prepared with the aid of an acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the Water-insoluble condition with retention of at least about 45% calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the Water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at elevated temperature with partial drying.

15. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said ma terial, by treating it with a solution of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which solution is freshly prepared with the aid of formic acid, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at elevated temperature. with p r ia y n l 16. A process for imparting to cotton fibrous. material selected from the group consisting of loose material, yarn, material .in an intermediate stage of conversion into yarn and fish netting, awater resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous: emulsion of a melamine formaldehyde condensation product of limited water solubility from 1 mol of melamine and about 3 mols of formaldehyde which emulsion contains also an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and re moving mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at about C. with partial drying.

17. A process for imparting to cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting, a water resistant impregnation protecting such material from attack by micro-organisms, without substantial change in the tensile strength of the said material, by treating it with an aqueous solution of a melamine formaldehyde condensation product of unlimited water solubility from 1. mol of melamine and about 2 mols of formaldehyde which solution also contains an ammonium salt of a strong acid as a hardening accelerator, which comprises after-impregnating the material and removing mechanically the excess of impregnating liquid, hardening the melamine formaldehyde condensation product in and upon the fibre into the waterinsoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until the resin condensation is completed, so that the condensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid, said hardening being carried out at about 80 C.

18. Cotton fibrous material protected from the attack by micro-organisms, without substantial change in the tensile strength of the said material, by a water resistant impregnation produced by impregnating the material with an aqueous impregnating liquid of a melamine formaldehyde condensation product which contains a hardening accelerator, removing mechanically the excess of impregnating liquid and hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45%, calculated on the weight of the fibrous material, of the water of the impregnating liquid until. the resin condensation is completed, so that the condensation into the Water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

19. Cotton fibrous material selected from the group consisting of loose material, yarn, material in an intermediate stage of conversion into yarn and fish netting protected from the attack by micro-organisms, without substantial change in the tensile strength of the said material, by a water resistant impregnation produced by impregnating the material with an aqueous impregnating liquid of a melamine formaldehyde condensation product which contains a hardening accelerator, removing mechanically the excess of impregnating liquid and hardening the melamine formaldehyde condensation product in and upon the fibre into the water-insoluble condition with retention of at least about 45 calculated on the Weight of the fibrous material, of the water of the impregnating liquid until the I 11 resin condensation is completed, so that the eondensation into the water insoluble state is actually conducted in the presence of water originating from the impregnating liquid.

References Cited in the file of this patent UNITED STATES PATENTS 12 Widmer et al. May 30, 1944 Pollard July 1, 1947 Jacoby Nov. 25, 1947 Dalton et al Mar. 20, 1951 Cohen July 24, 1951 Benignus Apr. 29, 1952 Gagarine June 19, 1953 FOREIGN PATENTS Great Britain Ian. 2, 1948 

1. A PROCESS FOR IMPARTING TO COTTON FIBROUS MATERIAL A WATER RESISTANT IMPREGNATION PROTECTING SUCH MATERIAL FROM ATTACK BY MICRO-ORGANISMS, WITHOUT SUBSTANTIAL CHANGE IN THE TENSILE STRENGTH OF THE SAID MATERIAL, BY TREATING IT WITH AN AQUEOUS IMPREGNATING LIQUID OF A MELAMINE FORMALDEHYDE CONDENSATION PRODUCT WHICH CONTAINS A HARDENING ACCELERATOR, WHICH COMPRISES AFTERIMPREGNATING THE MATERIAL AND REMOVING MECHANICALLY THE EXCESS OF IMPREGNATING LIQUID, HARDENING THE MELAMINE FORMALDEHYDE CONDENSATION PRODUCT IN AND UPON THE FIBRE INTO THE WATER-INSOLUBLE CONDITION WITH RETENTION OF AT LEAST ABOUT 45%, CALCULATED ON THE WEIGHT OF THE FIBROUS MATERIAL, OF THE WATER OF THE IMPREGNATING LIQUID UNTIL THE RESIN CONDENSATION IS COMPLETED, SO THAT THE CONDENSATION INTO THE WATER INSOLUBLE STATE IS ACTUALLY CONDUCTED IN THE PRESENCE TO WATER ORIGINATING FROM THE IMPREGNATING LIQUID. 